The invention relates to a field unit with a bus node which is designed for signal conversion between an external bus protocol for communication with a higher-level control device and an internal bus protocol for communication with at least one function module, in such a way that a sequential transmission of data packets is made along an internal bus system using the internal bus protocol, and also comprising function modules which are assigned to the bus node and are designed for processing of data packets transmitted over the internal bus system and for unidirectional or bidirectional signal transmission with at least one downstream function component. The invention also relates to a method for operating such an automation system.
In DE 10 2009 042 354 A1, communications are coordinated by means of a non-safe communication master, which generates and administers the routing information for the distribution of data packets between the safe bus participants. The selection of the routing information is made on the hardware side in the connected media.
In DE 10 2009 054 157 B3, the safe communication is provided at the field bus level.
In EP 1 927 914 A2, checking of the functioning of a bus system control unit is ensured by a safety module looped into the internal bus or into a separate bus.